In China, total Hg (Hg-T) and methylmercury (MeHg) were quantified in rice grain grown in three sites using water-saving rice cultivation methods, and in one Hg-contaminated site, where rice was grown under flooded conditions. Polished white rice concentrations of Hg-T (water-saving: 3.3 /- 1.6 ng/g; flooded: 110 /- 9.2 ng/g) and MeHg (water-saving 1.3 /- 0.56 ng/g; flooded: 12 /- 2.4 ng/g) were positively correlated with root-soil HgT and MeHg contents (HgT: r(2) = 0.97, MeHg: r(2) = 0.87, p < 0.05 for both), which suggested a portion of Hg species in rice grain was derived from the soil, and translocation of Hg species from soil to rice grain was independent of irrigation practices and Hg levels, although other factors may be important. Concentrations of HgT and other trace elements were significantly higher in unmilled brown rice (p<0.05), while MeHg content was similar (p > 0.20), indicating MeHg infiltrated the endosperm (i.e., white rice) more efficiently than inorganic Hg(II).

Methylmercury; Milled white rice; Translocation; Water-saving paddies

环境地球化学国家重点实验室; 水资源与水电工程科学国家重点实验室; Wuhan University; Chinese Academy of Science